Enterotoxigenic Escherichia coli (ETEC) diarrhea is hyperendemic among young Egyptian children, with an estimated cumulative incidence of 2.4 symptomatic ETEC episodes from birth to 36 months, and a balanced distribution of toxin phenotypes. These features make it logical to develop a field site for the evaluation of ETEC epidemiology and ETEC vaccines in Egypt. Recently, we have begun a collaborative project to develop a site in Abees (near Alexandria) for the study of pediatric diarrhea. This project will follow a pediatric cohort with the following aims: 1) to determine the age-specific incidence rate of ETEC diarrhea from birth to 35 months, by toxin and colonization factor (CFA) phenotype; 2) to ascertain the strength of attribution of diarrheal symptoms to fecal isolation of ETEC; 3) to evaluate the protective relationship between titers of serum IgG antibodies to ETEC toxins and CFAs and the risk of diarrhea due to ETEC manifesting these virulence factors. Work on this project began in June, 1993; the work thus far has focused on protocol design, data form development, development of computer systems for data entry and management, and preparation of manuals of procedures. It is anticipated that the cohort study will, after conduct of a pretest, begin in November, 1993.